Final answer:
A characteristic that indicates a polynomial is in standard form is that the leading term has the highest exponent. Hence the correct answer is option D
Step-by-step explanation:
In standard form, a fourth-degree polynomial satisfies the characteristic that the leading term has the highest exponent. The leading term is the term with the highest power of the variable. For example, a fourth-degree polynomial in standard form would have a leading term with an exponent of 4.
Option D, 'The leading term has the highest exponent,' is the characteristic that indicates a polynomial is in standard form.